Vapor recovery system

ABSTRACT

Vapor recovery system for recovering fuel vapors normally lost during the filling of tanks and including basically an absorber having associated therewith components to condition the vapor and liquid entering the absorber, to improve absorber efficiency, to reduce thermal losses and to improve system safety.

United States Patent Nichols 1451 Aug. 20, 1974 VAPOR RECOVERY SYSTEM Inventor:

Filed:

Richard A. Nichols, Santa Ana,

Calif.

Assignee: Parker Hannifin Corporation,

Cleveland, Ohio Dec. 6, 1971 Appl. No.: 205,054

US. Cl 62/54, 55/88, 55/89,

lnt. Cl. F170 13/12 Field of Search 62/54, 55.5, 125, 256,

227, 228; 220/85 VR, 85 VS, 150; 417/40;

References Cited UNITED STATES PATENTS 2,577,598 12/1951 Zwickl 62/125 X 2,765,872 10/1956 Hartman et a1 55/88 2,849,150 8/1958 Tompkins, .lr. 22(1/85 VR 3,266,262 8/1966 Moragne 62/54 3,449,922 6/1969 Ruff et a1 62/228 3,474,633 10/1969 Bailey 62/50 X 3,648,436 3/1972 Schonewald et a1. 55/88 3,661,366 5/1972 Shinkle 1 261/5 3,672,180 6/1972 Davis 1. 62/54 3,714,790 2/1973 Battey 62/54 Primary Examiner-Meyer Perlin Assistant Examiner-Rona1d C. Capossela Attorney, Agent, or Firm-Diller, Brown Ramik & Wight [5 7] ABSTRACT 39 Claims, 2 Drawing Figures VAPOR RECOVERY SYSTEM This invention relates to a highly efficient vapor recovery system primarily intended, but not so restricted, to recover vapors normally lost during the filling of tanks with fuel, primarily gasoline.

BACKGROUND OF INVENTION SUMMARY OF INVENTION In accordance with this invention, there has been developed a vapor recovery system which is not only highly safe, but also highly efficient in operation.

One feature of the system is a combined saturator and flash separator wherein liquid spray of the flash separator is utilized to saturate vapor thereby combining into one operation two previous operations.

Another feature of the invention is the provision of a two speed vapor compressor whereby maximum compressor efficiency is obtainable. Associated with the two speed compressor is a bypass system whereby the compressor is momentarily unloaded both during the starting thereof and during the change from low speed to high speed operation.

Another feature of the invention is the utilization of a water-glycol system for cooling both the vapor compressor and the refrigeration unit compressor with chilled liquid fuel draining from the absorber being utilized as the coolant for the system.

Yet another feature is a control system for controlling the liquid fuel level within the absorber as well as controls for preventing the undue draining of liquid fuel from both a storage tank and the absorber during periods of system shut down.

A further feature of the invention is an efficient saturator wherein incoming vent gases impinge against a wall of the saturator tank assuring saturation of all vent gases entering this system.

Yet a further feature of the invention is an efficient liquid fuel circulation system for the absorber.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the accompanying drawings wherein:

FIG. 1 is a schematic showing of various components of the vapor recovery system and connections therebetween, and

FIG. 2 is a fragmentary schematic of a modified portion of the vapor recovery system.

The vapor recovery system includes vapor recovery apparatus 5, saturator 6, compressor unit 8, absorber 9 and refrigeration unit 10. Suitable piping connects all of these components.

Fuel is stored in storage tank 11, preferably underground, with fuel therein at substantially constant temperature.

Fuel supply line 12 leads to tank filling area where tank 13, such as illustrated fuel transport truck, is

filled. Tank 13 has, either as part thereof or associated therewith, vapor recovery mechanism 14 connectible byhose 15 to vapor receiving apparatus 5.

Vapor receiving apparatus 5 includes elongated header 16 having check valves 17 for simultaneously servicing plurality of tanks 13. The check valves 17 also insure a unidirectional vapor flow from tanks 13 to vapor receiving apparatus 5. Conduit 18 couples header 16 to saturator 6.

SATURATOR Saturator 6 includes underground tank 20 having constant supply of liquid fuel therein. Excess liquid fuel is returned to tank 11 through return line 21 by return pump 22. Return line 21 has therein check valve 23 and shut-off valve 24.

Liquid level in tank 20 is maintained by HI-LO level switch 25 controlling operation of pump 22. HI-LO level safety switch 26 provides for disabling the system in event of failure of switch 25.

Tank 20 also has a safety vent 27 which may incorporate a safety pressure valve operating below 0.5 psig and above 0.8 psig.

Vent gases, which are under a slight pressure, flow into tank 20 through conduit 18 and are directed by spray head 28 against one wall of tank 20. Vent gases are impinged against the tank wall for uniform distribution so the gases will not channel in migrating through tank 20.

Vent gases flowing through tank 20 are saturated by means of liquid spray from flash separator spray head 29 through conduit 30 with saturator 6 also functioning as flash separator for liquid fuel being returned to tank 11.

Saturator 6 is underground for safety reasons as well as dual purpose reason of acting as a liquid drop out tank. At approximately -20F., vapor space of gasoline tanks having a liquid surface becomes explosive. With buried tank, temperatures remain high enough that this condition does not exist.

Saturated gases pass from saturator 6 through conduit 31 to compressor unit 8.

COMPRESSOR UNIT Compressor unit 8 includes compressor 33 driven by two speed motor 34. Compressor 33 is connected to conduit 31 through special conduit section 34 and filter 35. Compressed gases pass from compressor 33 through conduit 36 into finned tube aftercooler 37.

Vapor recirculating line 38 is connected to conduit section 34 through pressure controlled valve 40 'which opens to recirculate vapor to compressor when vapor pressure in conduit section 34 is less than 0.5 psig so that compressor need not be shut off.

Conduit section 34 is provided with pressure switches 41, 42 which respond to pressure at their location. Switch 41 turns on compressor at 0.5 psig to operate at low speed. Switch 42 operates at 0.75 psig to operate compressor at high speed.

Compressor unloading line 43 bypasses valve 40 and has solenoid control valve 44 controlling flow therethrough. Valve 44 opens for about 3 seconds between low speed and high speed operation permitting compressor 33 to come up to speed. Valve 44 is also open at time of compressor start up whereby compressor uses vapors that have been cooled. Thus, compressor inlet gas temperature cannot rise to a dangerously high level.

Conduit section 34 is also provided with low pressure compressor shut off switches 45, 46. Switch 45 shuts off the compressor in low speed when pressure is below about 0.05 psig and switch 46 functions to shut off the compressor in high speed when pressure is below about O.15 psig. Compressor 33 is also provided with conventional oil pressure and over temperature shut off switches (not shown).

Compressed vapors passing through aftercooler 37 are reduced in temperature to the point that they may be passed through liquid fuel aftercooler 47 from conduit 48 without the cooling liquid fuel being vaporized. Vapors are cooled in aftercooler 47 to ambient temperature and then passed by way of conduit 50 to perforated branched distributor bar 49 in absorber 9. Conduit 50 has liquid flow preventing bend 51 and check valve 52 therein in spaced relation. Conduit 38 is connected to conduit 50 between bend 51 and valve 52 and in addition to its bypass function serves to return liquid fuel from conduit 50 to tank through conduit section 34 and conduit 31.

In order to prevent liquid fuel from being drawn into compressor 33, particularly during start-up, a liquid drain line 132 extends from filter 35 to tank 20. Check valve 133 is positioned in line 132 above a float tank 134 having a float controlled switch 135 mounted therein and operable to shut down compressor 33 when liquid level in float tank 134 rises to a predetermined level. An orifice 136 is disposed in drain line 132 between float tank 134 and tank 20 whereby there is liquid accummulation in float tank 134 only when liquid drainage from filter 35 exceeds the capacity of orifice 136.

ABSORBER Absorber 9 includes tank 53 having dished bottom. Liquid fuel is maintained in tank 53 at predetermined level by drain line 54 which connects to line 50. Flow through drain line 54 is controlled by valve 55 further controlled by float valve 56. Overflow control line 57 leads from float valve 56 to valve 55 float valve 56 being of variable orifice type permitting increased flow through line 57in accordance with rise in level ofliquid fuel in tank 53. Bypass line 58 couples between lines 57 and 48 and has flow controlling orifice 60 therein. When flow through line 57 exceeds that permitted by orifice 60, valve 55 opens to allow liquid fuel to drain from tank 53 into line 30. By passing collected fuel from absorber 9 through saturator spray head 29 prior to return to tank 11, saturator 6 functions as flash separator to separate from liquid fuel entrained gases contained therein prior to pumping of liquid fuel to tank 11.

Static screen 59 is mounted in tank 53 always slightly below level of liquid therein with screen 59 being grounded to dissipate static charges.

Solenoid control valve 61 is mounted in line 57. Valve 61 is normally closed but it is opened during absorber operation, as described hereinafter.

Liquid fuel is supplied absorber 9 from tank 11 through line 62. Line 62 has manual valve 63 which is closed during an extended period of shut down of system. Line 62 leads to pump 64 having line 65 receiving fuel therefrom and delivering same to boost pump 66. Line 67 leads from pump 66 through heat exchanger 68 Line 73-has liquid fuel circulated therethrough by means of pump 74 to spray unit 75 mounted in upper part of tank 53. Line 76 has liquid fuel circulated therethrough from tank 53 by pump 77 to spray unit 78 also mounted in upper part of tank 53. Line 76 is coupled to chiller 80 of refrigeration unit 10 for cooling circulating liquid fuel. Suitable baffles overlie inlets of pipes 54, 73, 76 preventing entry of settling matter.

Processed gases (primarily air) are vented from tank 53 through line 81 leading down from top of tank. Flow through line 81 is controlled by pressure control valve 82 with exhausted gases passing through flame arrestor 83 prior to discharge. Drain line 84 connects to line 81 for removing any liquid which enters same.

Tank 53 also has fail-open safety relief valve 79 which opens at higher pressure than valve 82 and has a capacity considerably greater than maximum flow of compressor 33.

Water vapor contained in the vent gases from tank 13 and that contained in the liquid fuel condenses in absorber 9 and appears as ice due to the low temperature of liquid fuel in tank 53. Tank 53 has viewport 85 for viewing ice accumulation. However, suitable automatic detectors may be provided. Water is drained from tank 53 through drain line 86 controlled by manual valve 87 after temperature within absorber 9 has permitted to rise by operating system with refrigeration unit 10 shut down or otherwise heating tank 53 to melt ice.

REFRlGERATlON UNIT Refrigeration unit 10 includes freon compressor 90 with compressed gases being condenser in condensor 91 and expanded in chiller 80. Gases are cooled in condenser 91 by circulating liquid fuel from tank 11 therethrough by means of pump 64 through by-pass line 92, which is coupled to line 30 for circulating liquid fuel from condenser 91 through saturator 6.

Flow through line 92 is controlled by valve 93 having pressure control line 94 coupled to tank 53. Valve 93 closes when pump 64 shuts down to prevent gravity flow from tank 11 to saturator 6. Line 94 has solenoid valve 95 which opens when pump 64 runs to allow pressure in tank 53 to open valve 93.

Valve 96 in series with valve 93 is controlled by the outlet temperature of liquid fuel flowing from condenser 91. Valve 96 controls flow to prevent condenser freon temperature from falling below 50F.

WATER-GLYCOL SYSTEM Water-glycol system is provided for cooling compressors 33 and 90. System includes reservoir 97 having circulating pump 98 connected thereto for circulating water-glycol solution through circulating pump 100. Circulating solution passes through heat exchanger 101 where it is cooled by chilled liquid fuel draining from saturator 9. Circulating pipe has direct return to reservoir 97 with restricted orifice 102 controlling flow to reservoir 97. A first branch line 103 is connected to compressor 33 for cooling same with return line 104 extending between compressor 33 and reservoir 97. A

second branch pipe 105 leads to compressor 90 and return line 106 leads from compressor 90 to reservoir 97.

Although the water-glycol system is highly satisfacrory, it is also possible to substitute gasoline or similar fuel as the coolant medium in lieu of water-glycol.

OPERATION Vent gases from tank 13 being filled flow into header l6 and then into saturator 6 where saturation to a substantially non-explosive mixture is assured. Combined saturator and flash separator 6 operates at a pressure of between 0. l 5 psig and 0.75 psig. Gases are drawn from saturator 6 by compressor 33 which delivers gases at 50 psig and 300F. to aftercooler 37. Cooled gases pass into absorber 9 through gas check valve 52 which allows vapor to be pump into absorber when compressor pressure exceeds absorber pressure and prevents liquid from leaving the absorber through gas inlet when compressor 33 is not operating. Compressed vapor is distributed in absorber 9 below the level of liquid fuel therein by distributor 49. Vapor is introduced into liquid fuel in the form of large diameter bubbles which rise quickly through the liquid fuel although the vapor is cooled and some mass transfer occurs.

The main heat and mass transfer occurs in the spray section where upwardly moving vapor is thoroughly washed with massive spray of small droplets from spray heads 75, 78. Droplet diameter is small so that drops have a large area to volume ratio. Absorber 9 is sized so that gas velocity in the absorber will not entrain a 0.0005 inch drop by Stokes law in the outlet flow stream. Gas vapor passing through the spray section collects at top of tank 53 and are exhausted.

Collected liquid fuel, together with liquid fuel added to absorber 9 from tank 11, passes through heat exchanger 68 and cools liquid fuel being delivered from tank 11 to absorber 9'. Returning liquid fuel next passes through aftercooler 47 to cool compressed vapors. Finally, returning liquid fuel passes through heat exchanger 101 to cool the water-glycol solution.

Pump 64 and boost pump 66 deliver liquid fuel from tank 11 to absorber 9 at a pressure of 56 psig to overcome pressure of 50 psig in tank 53.

The refrigerating of liquid fuel circulating through refrigeration unit and the volume of flow is such that temperature within absorber 9 is on the order of 10F. to l 0F. A typical installation would have the temperature of liquid fuel in tank 53 at 0F. with the refrigerated fuel returning into the upper part of tank 53 having a temperature on the order of lOF.

MODIFIED FORM In FIG. 2 there is illustrated a vapor storage tank 7 which is connected to conduit 31 for accumulating saturated vapors during the time of low vapor flow from saturator 6 thereby limiting the time of operation of the compressor to one where an ample supply of vapors are available thereby providing for maximum compressor efficiency. The various control switches 41, 42 and 45, 46 normally will be eliminated from conduit section 34, as shown in FIG. 2, and a single capacity compressor 110 may be utilized.

Operation of compressor 110 is primarily controlled by switches 111, 112 associated with a bladder 113 of vapor storage tank 7. Bladder 113 expands and contracts in accordance with the volume of vapor in storage tank 7. When bladder 113 reaches a predetermined upper level, spaced from the top of tank 7, switch 112 is actuated to initiate operation of compressor 110. Compressor will operate until bladder 113 reaches a predetermined lower position where switch 111 is no longer actuated and compressor 110 is shut off.

If desired, conduit section may be provided with control switches such as or similar to switches 41, 42 and 45, 46 and the compressor may be a dual capacity compressor such as compressor unit 8. Switches 111, 112 may then either be omitted or incorporated in circuits with switches 41, 42 and 45, 46.

It is to be understood that the proportions of the components shown in the drawings have been exaggerated for clarity purposes.

Although only two perferred embodiments of the invention have been specifically illustrated and described herein, it is to be understood that minor variations may be made in the vapor recovery system without departing from the spirit and scope of the invention, as defined in the appended claims.

What is claimed as new is:

l. A vapor recovery system of the type including a compressor and an absorber connected to said compressor for receiving compressed vapors therefrom,

and wherein received vapors are recovered as liquid in said absorber subsequent to being compressed by said compressor, and recovered liquid is collected and stored; and combined saturator and flash separator means for saturating received vapors in advance of said compressor and for separating gases from collected liquid prior to storage of the collected liquid.

2. The vapor recovery system of claim 1 wherein said combined saturator and flash separator means includes vapor and entrained liquid receiving means, liquid collecting means, and spray means for spraying collected liquid in the presence of collected vapor and for simultaneously releasing gases entrained in the recovered liquid and saturating the received vapors.

3. The vapor recovery system of claim 1 wherein said combined staturator and flash separator means includes a tank, means for maintaining a substantially constant level of liquid therein, means for distributing collected vapors in said tank, and spray means in said tank above said liquid level and connected to a discharge line from said absorber for spraying liquid from said absorber for saturating vapors within said tank.

4. The vapor recovery system of claim 3 wherein said means for distributing vapors includes spray means for impinging vapors against a vertical wall of said tank.

5. The vapor recovery system of claim 3 wherein said tank has safety vent means operable under both low pressure and high pressure conditions to vent said tank.

6. In a vapor recovery system of the type wherein received vapors are compressed and then passed to an absorber, compressor means for selectively operating at different capacities, said compressor means having inlet means for receiving received vapors and outlet means coupled to said absorber for directing compressed vapors towards said absorber, and control means for operating said compressor at a capacity in accordance with the availability of collected vapors.

7. The vapor recovery system of claim 6 wherein said control means include inlet pressure switches in said inlet means and separately operable at different inlet pressure for automatically selecting the operating capacity of said compressor means, and further inlet pressure switch means in said inlet means for shutting down said compressor in response to abnormal inlet pressures.

8. The vapor recovery system of claim 6 wherein said control means include inlet pressure switches in said inlet means and separately operable at different inlet pressure for automatically selecting the operating capacity of said compressor means.

9. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable in response to a low pressure in said compressor inlet means.

10. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable during the starting of said compressor to release back pressure thereon.

11. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable during the shifting of said compressor means from one operating capacity to a higher operating capacity.

12. In a vapor recovery system, a saturator for receiving collected vapors and enriching the same, a compressor, an absorber, a first conduit between said saturator and said compressor for delivering enriched vapors from said saturator to said compressor and second conduit between said compressor and said absorber means for delivering compressed vapors from said compressor to said absorber, and return conduit means between said second conduit at a first point adjacent said absorber and said first conduit at a second point adjacent said compressor, and said first conduit being in gravity communication with said saturator from said second point for directing liquid accidentally returned through said return conduit to said saturator.

13. The vapor recovery system of claim 12 together with a pressurized vapor actuated check valve in said second conduit between said first point and said absorber for normally preventing the back flow of liquid from said absorber through said second conduit.

14. In a vapor recovery system, an absorber having a recirculating liquid spray system, said absorber including a tank having a liquid supply in a lower portion thereof and a head space above said liquid supply, and said spray system including a first spray means in said head space, first means for withdrawing liquid from said liquid supply and supplying the same to said first spray means, means for refrigerating said withdrawn liquid whereby liquid temperature within said tank is reduced materially below ambient temperature, second spray means in said head space, and second means for withdrawing liquid from said liquid supply and supplying same to said second spray means.

15. In a vapor recovery system, an absorber, a drain line connected to said absorber for removing excess liquid therefrom, and valve means for controlling flow through said drain line and maintaining a substantially constant liquid level in said absorber, said valve means including a fluid responsive valve in said drain line, a control line from said absorber to said valve, and flow control means in said absorber for permitting liquid flow from said absorber through said control line when an over level liquid condition exists in said absorber.

16. The vapor recovery system of claim 15 wherein said control line has a control branch leading into said drain line downstream of said valve, said control branch having a restricted flow as compared to said control line.

17. The vapor recovery system of claim 15 wherein said flow control means includes a float actuated valve means for varying flow into said control line in accordance with the level of liquid in said absorber.

18. The vapor recovery system of claim 15 together with a valve in said control line for closing said control line during periods of system shut down.

19. In a vapor recovery system, a liquid supply tank, an absorber, a recirculating spray system for said absorber including a refrigeration unit having a condenser, a supply line from said tank and a return line to said tank, pump means in said supply line, said supply line being branched and having one branch connected to said absorber for supplying liquid thereto, a second branch of said supply line being connected to said condenser for supplying liquid thereto as a coolant, a liquid return connection between said condenser and said return line bypassing said absorber, and flow control means in said second branch.

20. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to the temperature of refrigerant in said condenser.

21. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to pressure in said absorber.

22. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to pressure in said absorber, and includes a control line between said valve and said absorber, and a valve in said control line operable only during operation of said pump.

23. The vapor recovery system of claim 19 wherein a booster pump is incorporated in said one branch for pressurizing liquid from said supply tank above the operating pressure of said absorber.

24. The vapor recovery system of claim 19 wherein said return line has incorporated therein a flash separator for removing entrained gases from returning liquid from said absorber.

25. In a vapor recovery system, an absorber, a refrigeration unit for cooling liquid within said absorber, said refrigeration unit including a refrigerant compressor, a

' vapor compressor for compressing and supplying vapors to said absorber under pressure, and a single separate cooling system for said two compressors.

26. The vapor recovery system of claim 25 wherein said cooling system is a water-glycol system.

27. The vapor recovery system of claim 25 wherein said cooling system includes a heat exchanger utilizing as a coolant liquid flowing from said absorber.

28; The vapor recovery system of claim 27 wherein said heat exchanger is connected in series with a second heat exchanger downstream thereof for cooling compressed vapors.

29. The vapor recovery system of claim 28 wherein liquid is supplied said absorber from a storage tank through a third heat exchanger connected in series with said first mentioned heat exchanger, and upstream of said second heat exchanger.

30. The vapor recovery system of claim 27 wherein said heat exchanger is connected in series with a second heat exchanger for cooling compressed vapors.

31. The vapor recovery system of claim 30 wherein liquid is supplied said absorber from a storage tank through a third heat exchanger connected in series with said first mentioned heat exchanger.

32. The vapor recovery system of claim 25 wherein said cooling system includes a coolant reservoir, a heat exchanger, a circulating pump for circulating coolant through said heat exchanger, a branch line from said heat exchanger to each of said compressors.

33. The vapor recovery system of claim 32 wherein there is a further branch line leading back to said reservoir and having flow restricting means therein.

34. In a vapor recovery system, an absorber, said absorber having vent means for venting gases separated from recovered vapor, said vent means including a vent line leading downwardly from an upper part of said absorber, a pressure release valve connected to a lower part of said vent line, and a liquid return line connected to said vent line upstream of said valve and opening into said absorber for returning liquid passing into said vent line to said absorber.

35. In a volatile vapor recovery system, an absorber for collected volatile vapor including a tank, means for maintaining volatile liquid at a generally predetermined level in said tank, means for directing compressed collected volatile vapors into said tank below said predetermined level for flow upwardly into said tank above said predetermined level and a static screen within said tank slightly below said predetermined level at a position adjacent thereto and above said means for directing compressed collected volatile vapors into said tank, said static screen being grounded to dissipate static charges.

36. In a vapor recovery system, a compressor, a conduit connected to said compressor for supplying vapors to said compressor, liquid trap means in said conduit in advance of said compressor, a drain line connected to said trap means for draining off trapped liquid, and switch means operable by draining liquid for controlling the operation of said compressor.

37. The vapor recovery system of claim 36 wherein said drain line has a restrictor therein for limiting liquid flow therethrough.

38. The vapor recovery system of claim 36 wherein said drain line has a restrictor therein for limiting liquid flow therethrough, and a float tank for receiving excess liquid, and said switch means are responsive to liquid level in said float tank.

39. In a vapor recovery system, vapor receiving means, a compressor, conduit means between said vapor receiving means and said compressor for deliverying vapor from said receiving means to said compressor, a vapor storage tank connected to said conduit means for receiving and storing vapors, and switch means associated with said vapor storage tank for controlling the operation of said compressor in accordance with the volume solely of vapors in said vapor storage tank, said vapor storage tank including a readily yieldable and movable internal bladder and said switch means being mechanical in nature and operable by direct contact by said bladder during the movement 

1. A vapor recovery system of the type including a compressor and an absorber connected to said compressor for receiving compressed vapors therefrom, and wherein received vapors are recovered as liquid in said absorber subsequent to being compressed by said compressor, and recovered liquid is collected and stored; and combined saturator and flash separator means for saturating received vapors in advance of said compressor and for separating gases from collected liquid prior to storage of the collected liquid.
 2. The vapor recovery system of claim 1 wherein said combined saturator and flash separator means includes vapor and entrained liquid receiving means, liquid collecting means, and spray means for spraying collected liquid in the presence of collected vapor and for simultaneously releasing gases entrained in the recovered liquid and saturating the received vapors.
 3. The vapor recovery system of claim 1 wherein said combined staturator and flash separator means includes a tank, means for maintaining a substantially constant level of liquid therein, means for distributing collected vapors in said tank, and spray means in said tank above said liquid level and connected to a discharge line from said absorber for spraying liquid from said absorber for saturating vapors within said tank.
 4. The vapor recovery system of claim 3 whereIn said means for distributing vapors includes spray means for impinging vapors against a vertical wall of said tank.
 5. The vapor recovery system of claim 3 wherein said tank has safety vent means operable under both low pressure and high pressure conditions to vent said tank.
 6. In a vapor recovery system of the type wherein received vapors are compressed and then passed to an absorber, compressor means for selectively operating at different capacities, said compressor means having inlet means for receiving received vapors and outlet means coupled to said absorber for directing compressed vapors towards said absorber, and control means for operating said compressor at a capacity in accordance with the availability of collected vapors.
 7. The vapor recovery system of claim 6 wherein said control means include inlet pressure switches in said inlet means and separately operable at different inlet pressure for automatically selecting the operating capacity of said compressor means, and further inlet pressure switch means in said inlet means for shutting down said compressor in response to abnormal inlet pressures.
 8. The vapor recovery system of claim 6 wherein said control means include inlet pressure switches in said inlet means and separately operable at different inlet pressure for automatically selecting the operating capacity of said compressor means.
 9. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable in response to a low pressure in said compressor inlet means.
 10. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable during the starting of said compressor to release back pressure thereon.
 11. The vapor recovery system of claim 8 together with conduit means for selectively recirculating compressed vapors to said inlet means of said compressor means, and valve means in said conduit means openable during the shifting of said compressor means from one operating capacity to a higher operating capacity.
 12. In a vapor recovery system, a saturator for receiving collected vapors and enriching the same, a compressor, an absorber, a first conduit between said saturator and said compressor for delivering enriched vapors from said saturator to said compressor and second conduit between said compressor and said absorber means for delivering compressed vapors from said compressor to said absorber, and return conduit means between said second conduit at a first point adjacent said absorber and said first conduit at a second point adjacent said compressor, and said first conduit being in gravity communication with said saturator from said second point for directing liquid accidentally returned through said return conduit to said saturator.
 13. The vapor recovery system of claim 12 together with a pressurized vapor actuated check valve in said second conduit between said first point and said absorber for normally preventing the back flow of liquid from said absorber through said second conduit.
 14. In a vapor recovery system, an absorber having a recirculating liquid spray system, said absorber including a tank having a liquid supply in a lower portion thereof and a head space above said liquid supply, and said spray system including a first spray means in said head space, first means for withdrawing liquid from said liquid supply and supplying the same to said first spray means, means for refrigerating said withdrawn liquid whereby liquid temperature within said tank is reduced materially below ambient temperature, second spray means in said head space, and second means for withdrawing liquid from said liquid supply and supplying same to said second spray means.
 15. In a vapor recovery system, an absorber, a drain line connected to said absorber for removIng excess liquid therefrom, and valve means for controlling flow through said drain line and maintaining a substantially constant liquid level in said absorber, said valve means including a fluid responsive valve in said drain line, a control line from said absorber to said valve, and flow control means in said absorber for permitting liquid flow from said absorber through said control line when an over level liquid condition exists in said absorber.
 16. The vapor recovery system of claim 15 wherein said control line has a control branch leading into said drain line downstream of said valve, said control branch having a restricted flow as compared to said control line.
 17. The vapor recovery system of claim 15 wherein said flow control means includes a float actuated valve means for varying flow into said control line in accordance with the level of liquid in said absorber.
 18. The vapor recovery system of claim 15 together with a valve in said control line for closing said control line during periods of system shut down.
 19. In a vapor recovery system, a liquid supply tank, an absorber, a recirculating spray system for said absorber including a refrigeration unit having a condenser, a supply line from said tank and a return line to said tank, pump means in said supply line, said supply line being branched and having one branch connected to said absorber for supplying liquid thereto, a second branch of said supply line being connected to said condenser for supplying liquid thereto as a coolant, a liquid return connection between said condenser and said return line bypassing said absorber, and flow control means in said second branch.
 20. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to the temperature of refrigerant in said condenser.
 21. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to pressure in said absorber.
 22. The vapor recovery system of claim 19 wherein said flow control means includes a valve responsive to pressure in said absorber, and includes a control line between said valve and said absorber, and a valve in said control line operable only during operation of said pump.
 23. The vapor recovery system of claim 19 wherein a booster pump is incorporated in said one branch for pressurizing liquid from said supply tank above the operating pressure of said absorber.
 24. The vapor recovery system of claim 19 wherein said return line has incorporated therein a flash separator for removing entrained gases from returning liquid from said absorber.
 25. In a vapor recovery system, an absorber, a refrigeration unit for cooling liquid within said absorber, said refrigeration unit including a refrigerant compressor, a vapor compressor for compressing and supplying vapors to said absorber under pressure, and a single separate cooling system for said two compressors.
 26. The vapor recovery system of claim 25 wherein said cooling system is a water-glycol system.
 27. The vapor recovery system of claim 25 wherein said cooling system includes a heat exchanger utilizing as a coolant liquid flowing from said absorber.
 28. The vapor recovery system of claim 27 wherein said heat exchanger is connected in series with a second heat exchanger downstream thereof for cooling compressed vapors.
 29. The vapor recovery system of claim 28 wherein liquid is supplied said absorber from a storage tank through a third heat exchanger connected in series with said first mentioned heat exchanger, and upstream of said second heat exchanger.
 30. The vapor recovery system of claim 27 wherein said heat exchanger is connected in series with a second heat exchanger for cooling compressed vapors.
 31. The vapor recovery system of claim 30 wherein liquid is supplied said absorber from a storage tank through a third heat exchanger connected in series with said first mentioned heat exchanger.
 32. The vapor recovery system of claim 25 wherein said cooling systeM includes a coolant reservoir, a heat exchanger, a circulating pump for circulating coolant through said heat exchanger, a branch line from said heat exchanger to each of said compressors.
 33. The vapor recovery system of claim 32 wherein there is a further branch line leading back to said reservoir and having flow restricting means therein.
 34. In a vapor recovery system, an absorber, said absorber having vent means for venting gases separated from recovered vapor, said vent means including a vent line leading downwardly from an upper part of said absorber, a pressure release valve connected to a lower part of said vent line, and a liquid return line connected to said vent line upstream of said valve and opening into said absorber for returning liquid passing into said vent line to said absorber.
 35. In a volatile vapor recovery system, an absorber for collected volatile vapor including a tank, means for maintaining volatile liquid at a generally predetermined level in said tank, means for directing compressed collected volatile vapors into said tank below said predetermined level for flow upwardly into said tank above said predetermined level and a static screen within said tank slightly below said predetermined level at a position adjacent thereto and above said means for directing compressed collected volatile vapors into said tank, said static screen being grounded to dissipate static charges.
 36. In a vapor recovery system, a compressor, a conduit connected to said compressor for supplying vapors to said compressor, liquid trap means in said conduit in advance of said compressor, a drain line connected to said trap means for draining off trapped liquid, and switch means operable by draining liquid for controlling the operation of said compressor.
 37. The vapor recovery system of claim 36 wherein said drain line has a restrictor therein for limiting liquid flow therethrough.
 38. The vapor recovery system of claim 36 wherein said drain line has a restrictor therein for limiting liquid flow therethrough, and a float tank for receiving excess liquid, and said switch means are responsive to liquid level in said float tank.
 39. In a vapor recovery system, vapor receiving means, a compressor, conduit means between said vapor receiving means and said compressor for deliverying vapor from said receiving means to said compressor, a vapor storage tank connected to said conduit means for receiving and storing vapors, and switch means associated with said vapor storage tank for controlling the operation of said compressor in accordance with the volume solely of vapors in said vapor storage tank, said vapor storage tank including a readily yieldable and movable internal bladder and said switch means being mechanical in nature and operable by direct contact by said bladder during the movement thereof. 